Well flow circulating methods

ABSTRACT

A system and method for pumping tools into and out of a well through fluid circulation passages in the well including fluid input and return passages communicating with each other in the well bore and with surface apparatus for controlling fluid flow through said passages. The surface apparatus includes a manifold system for directing flow through the well circulation passages in either direction and includes variable choke means in the fluid return portion of the manifold for a controlled back pressure on the well passages and pressure and flow rate measuring means for monitoring fluid flow in the well passages.

United States Patent [151 3,637,012 Sizer et al. 1 Jan. 25, 1972 [54] WELL FLOW CIRCULATING 1,699,227 1/1929 Craddock ..166/91 UX ET O 3,090,439 /1963 Copland et al... 73/155 X 2,230,830 2/1941 Coberly ...l66/l53 UX [72] Inventors: Phillip S. Sizer, Dallas; Harry E. Schweg- 3,381,753 5/1968 Fredd ..166/l54 X man, Richardson, both of Tex. [73] Assignee- Otis Engineering Corporation Dallas Tex Primary Examiner lan A'Calven Attorney-E. Hastings Ackley [22] Filed: Oct. 20, 1969 [211 App]. No.: 870,617 [57] ABSTRACT A system and method for pumping tools into and out ofa well Related [IS-Application Data through fluid circulation passages in the well including fluid [62] Division of Sen No 682,874, Nov' 14, 1967. Pat. No input and return passages communicating with each other in the well bore and with surface apparatus for controlling fluid flow through said passages. The surface apparatus includes a manifold system for directing flow through the well circulation 52 US. Cl 1 Int Cl 52 passages in either direction and includes variable choke means [58] Fieid 315 70 6 153 3/12 in the fluid return portion of the manifold for a controlled 166/250 i back pressure on the well passages and pressure and flow rate I155 391 measuring means for monitoring fluid flow in the well [56] References Cited passages UNITED STATES PATENTS l2 C|8lmS, 9 Drawlng Figures 2,772,738 12/1956 Tausch .....166/3l4 L 62 i 32 zzfi 4a ,50 a M6 22- is 2w 30a 3/ 20 m 33 M. Wham PATENTED mam SHEET 1 BF 3 M M Y mm 0 m E N 9. g a m r g m g a e Em A I? III I m l! w R Nw mm P0 R m a ww .WW Ewm w w fi M h Wm \M hm Q. NM w PH SHEET 2 OF 3 w 7 Flg. 3 I i 73 um /05 7/ m5 642 ;1 41 4 s41, 10/ q;

1 z I e1 54 l Z, M; 5/3 h 6 O o I 105,403 6/) 55 a 53 F N h 35 pi 52 6 5 H- r. m q w MM 3 Ill? 6 I I [M W! ag}?! 32 32C H02 1 n r155 43k 74 30b 7 g VEXEZBRS 50 4 I05 IN (E I m 43 Phillip S. Sizer ml 4 2/ Harry E. Schweqmon ATTORNEY WELL FLOW CIRCULATING METHODS This application is a division of our copending application, Ser. No. 682,874, filed Nov. 14, 1967, for Apparatus For Pumping Tools Into And Out Of A Well.

This invention relates to well tools and more particularly relates to a method for pumping tools into and out of a well through fluid circulation passages within the well.

It is another object of the invention to provide a new and improved method of pumping well tools into and out of a well.

It is an additional object of the invention to provide a method of operating a well having supply and return fluid flow passages in said well connected with a surface manifold for supplying fluid under controlled conditions to the well flow passages for flow in either direction in the well through the passages.

It is a further object of the invention to provide a method of operating a well having a surface manifold system for fluid supply to and return from a well flow system including manual and automatic choke means for imposing a controlled back pressure on the well system.

It is still another object of the invention to provide a method of operating a well by the steps of supplying fluid to and returning fluid from a well in a closed circuit well flow circulation passage system including the further steps of determining the pressure and flow rate of fluid flowing through the manifold system into and returning from the well system.

It is another object of the invention to provide a method of fluid circulation in a well wherein fluid is neither produced from nor displaced into formations penetrated by the well.

Additional objects and advantages of the invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention and reference to the accompanying drawings thereof, wherein:

FIG. 1 is a schematic view of a well system for carrying out the method of the invention showing a fluid circulation control manifold with its valves positioned for pumping fluids into a well in one tubing string and returning the fluid in another communicating tubing string;

FIG. 1A is a fragmentary schematic view of an alternate form of fluid circulation control manifold with its valves positioned to direct fluids along the same flow pattern as the manifold shown in FIG. 1;

FIG. 2 is a fragmentary schematic view similar to FIG. 1 illustrating the valves of the manifold of the system positioned for fluid flow in the tubing strings in a direction opposite to that of FIG. 1;

FIG. 2A is a fragmentary schematic view of the manifold of FIG. 1A with the valves adjusted to direct fluids in a direction opposite to that of FIG. 1A;

FIG. 3 is a side view in elevation of a portable surface manifold unit for use in practicing the method of the invention and schematically showing metering and recording units connected therewith for determining pressures and flow rates within the system;

FIG. 4 is a top view in elevation of the manifold unit of FIG.

FIG. 5 is a left end view of the manifold unit of FIGS. 3 and FIG. 6 is a longitudinal top view, partly in section and partly in elevation, of the automatic choke used in the manifold unit; and,

FIG. 7 is a further enlarged view in section of the choke of FIG. 6 taken on the line 7-7 of FIG. 6.

Referring to the drawings, a well system embodying the invention includes a manifold 21 shown in a specific compact form in FIGS. 35, connected between a storage tank 22 and a well 23 equipped with tubing strings 24 and 25 interconnected within the well below a packer 26. The tubing strings communicate near their lower ends through a crossover connection 27 which permits fluid communication in either direction between the tubing strings. The tubing string 24 includes a suitable landing nipple 28 at its lower end below the crossover connection in which a bottom plug, not shown, is releasably locked for closing the lower end of the tubing string. Similarly, the tubing string 25 has a landing nipple 29 which releasably supports safety and check valve apparatus, not shown, below the crossover connection so that fluids entering the well through the casing perforations 23a may flow into the lower end of the tubing 25. The check valve prevents flow from the tubing string into the well, while the safety valve closes the tubing string responsive to excessive well pressure and other predetermined well conditions.

The tubing strings 24 and 25, with the crossover 27, provide a U-tube flow passage pattern in the well allowing fluid circulation from the surface and return for pumping well tools into and out of the well in the tubing strings. For example, well tools such as the bottom plug and the safety and check valve apparatus in the landing nipples of the tubing strings may be installed or removed by such pumping procedures. These procedures are especially useful in underwater or other relatively inaccessible oil wells where installation and removal of tools are accomplished from remote control stations. Equipment used in such procedures is illustrated and described at pages 3,779-3,78l of the Composite Catalog of Oil Field Equipment and Services, 1966-67 Edition, published by World Oil, Houston, Tex.

The fluid storage tank 22 is connected by a conduit line 30 having a pump 31 connected therein into an input line 30a of the manifold 21. A return or discharge line 32 of the manifold is connected into a separator 32a having a discharge line 32b leading back to the storage tank. A flowmeter readout panel 33 and a recorder 34 are connected with the manifold for indicating input and return flow rates and recording pressure conditions and total input in the system. The readout panel and recorder are connected together by a conductor 34a. Fluid is supplied from the tank through the manifold into one of the tubing strings of the well and returned through the other tubing string and manifold to the tank. The fluid is pumped into the well through either of the tubing strings while being returned from the well through the other tubing string for various well-servicing purposes including pumping well tools into and out of the well in the tubing strings.

The manifold 21 includes a manual choke 35 and an automatic choke 36 for manual and automatic control of the back pressure on fluid returning from the well through the manifold to the tank, for providing either manual or automatic control of the fluid pressure within the tubing strings in the well, which is particularly important in certain well procedures in which it is preferred that fluids be neither displaced into formations communicating with the well or produced from such formations.

A direct reading pressure gauge 40 is connected in the input line 30 for indicating the pressure of liquids being supplied to the well through the manifold 21. The pressure recorder 34 communicates with input and return line portions of the manifold by lines 41 and 41a, respectively. The lines 41 and 41a are connected together by a two position, three-way valve 41b so that the recorder is selectively communicated with either the input or return pressure in the manifold. A flowmeter 42 included in the input line 30a is connected with the panel 33 by a conductor 42a for measuring and indicating the flow rate from the tank 22 to the manifold.

The manifold 21 includes a conduit line 43 connected at one end to the input line 30a and at the other end to a discharge-retum line 43a leading to a suitable lubricator or chamber 44 which has a removable pressuretight end cap 45 to permit well tools to be inserted into and removed from the lubricator. The lubricator is connected into the flow line 24a connected to the tubing 24 so that a well tool is pumped from the lubricator through the flow line into the tubing in the well and returned from the well tubing through the flow line into the lubricator. The line 43 has a valve 50 for controlling flow therethrough. A first connector line 51 having a valve 52 therein is connected with the line 43 between the valve 50 and the line 43a. A second connector line 53 having a valve 54 therein is connected with the line 43 between the valve 50 and the input line 30a, so that flow in the input line 30 is directed into either the line 43 or the line 53. The connector lines 51 and 53 are connected into opposite ends of a third connector line 55 having a valve 60 therein. A discharge-retum line 61 of the manifold is connected at one end with the lines 53 and 55 between the valves 54 and 60 and at its other end with a suitable lubricator or chamber 62 which is connected to the flow 25a connected to the well tubing 25. The lubricator has a removable pressuretight end cap 63 for sealing its free end, through which well tools are inserted into and removed from the lubricator and the flow line with which it is connected.

A return or discharge conduit line 64 of the manifold is connected at one end with the lines 51 and 53 between the valves 52 and 60 and at its other end with branch lines 64a and 64b which are in turn connected to each other and to the discharge line 32 which is connected into the usual liquid-gas separator 32a. The line 32b connects the separator with the storage tank 22. The branch line or portion 64a has the automatic choke 36 connected therein and the branch line or portion 64b has the manual choke 35 connected in it. A flowmeter 65 is connected in the line 64 and to the readout panel 33 by a conductor 65a for measuring and indicating the rate of return flow from the manifold into the return discharge line 32 to the tank 22. The branch return line portions 64a and 64b include valves 70 and 71, respectively, so that flow in the line 64 to the line 32 is diverted through either branch to utilize either the manual or the automatic choke, as will be explained hereinafter.

The line 51 and its valve 52, and the line 55 and its valve 60, together with line 53 and its valve 54, thus provide flow conduit means for flow connecting the input line 30a and conduit line 43 with the flow line 24a and tubing string 24, and for connecting the tubing string 25 and flow line 25a and the return line 61 with the return conduit line 64 with discharge line 32 and the storage tank 22. Similarly, as shown in FIG. 2, the input line 30a may be connected by way of the connector line 53 with the line 61, the flow line 25a and the tubing 25, while the tubing 24 and flow line 24a are connected by way of the connector line 51 with the return conduit line 64 and discharge line 32 and tank 22, to provide reverse circulation through the system.

A conduit 72 connected with the automatic choke 36 has branch portions 720 and 72b extending from a two-position three-way valve 74 to the lines 64 and 30, respectively, whereby the choke is selectively operable responsive to either manifold input or return fluid pressure present in such lines.

One form of the automatic choke 36 is shown in FIGS. 6 and 7 and includes a tubular body 80 having a lateral inlet port 81 and a longitudinal discharge bore or passage 82 at one end. A plunger-type valve assembly 83 including a valve member 84 and a stem 85 having a bore 85a is disposed within the choke body 80 for longitudinal movement relative to an annular valve seat 90 secured within the body between the inlet port 81 and the discharge passage 82 for controlling the fluid flow through the choke. The valve plunger assembly is biased toward a closed position by a spring 91 and toward an open position by the force of control fluid pressure supplied through the conduit 72 from the input or return lines of the manifold into an annular chamber 92 in the choke body around the valve stem. The control fluid pressure acts around the valve stem on an annular area defined by spaced ring seals 93 and 94 within the choke body which seal around portions ofthe valve stem of different diameters.

The choke 36 is connected in the branch or return line portion 64a of the manifold 21 on the downstream side of the valve 70 so that when the valve 71 in the branch line portion 64b is closed and the valve 70 is open, returning fluid from the line 65 is diverted through the valve 70 into the inlet port 81 of the automatic choke. The return fluid flows through the choke body between the seat and valve member through the passage 82 into the portion of the branch line 64a downstream of the choke. The fluid flows through the discharge line 32 of the manifold and the separator 32a to the tank 22. The choke is adjusted by compressing the spring 91 to maintain a predetermined back pressure through the manifold into the well system. The choke performs a regulating function by constantly adjusting the back pressure responsive to the fluid pressure in either the input line 30a or the return line 64 of the manifold.

The well system 23, including the manifold 21, is useful for a number of procedures in a well involving both pumping fluids through the well and also displacing well tools into and returning them from a well. By way of example, one particular method which may be carried out in the well system is the pumping of a well too] from the lubricator 44 through the flow line 24a and the tubing string 24 into the landing nipple 28 at the lower end of the tubing string.

Assuming that the well is producing formation fluids, it is preferred that the well be first "shut-in" or killed" to establish substantially static or stable conditions within the well. The useful methods of providing a hydrostatic pressure at the bottom of the well equal to the formation pressure are employed, which includes filling the tubing strings 24 and 25 with a weighting liquid such as oil or water of sufficient density to overcome formation pressure at the bottom of the well. Also, a less dense liquid for only partially overcoming formation pressures may be used in conjunction with holding a back pressure on the well at the surface to stabilize the well and shut it in. The flow pattern illustrated by the arrows in FIG. 1 is used for circulating the fluid through and filling the tubing strings. For fluid flow into the tubing string 24 of the well from the tank 22 through the manifold and the flow line 24a, the valves 52 and 54 in the connector lines 51 and 53, respectively, are closed. The valve 50 in the line 43 is open so that fluid pumped from the tank 22 through the line 30 by the pump 31 is delivered into the manifold input line 30a from which it flows through the line 43, the open valve 50, and into the line 43a. The closed valves 52 and 54 restrict the flow to the line 43 so that it must pass directly into the line 43a connected with the lubricator 44. The fluid flows through the lubricator and flow line 24a into and downwardly in the tubing string 24. At the lower end of the tubing string 24 the fluid crosses over in the device 27 into the lower end of the other tubing string 25.

For return through the manifold of the fluid from the well in the tubing string 25 and flow line 25a, the valve 60 in the connector line 55 is open and since the valves 52 and 54 are already clo sed, as explained above, fluid from the line 61 is restricted to flow through the connector line 55 into the return line 64. The fluid flows upwardly in the tubing string 25 through the flow line 25a into the lubricator 62 from which the fluid enters the line 61. The fluid flows from the line 61 into the connector line 55 and through the open valve 60 into the return line 64 and the line 32 to the tank 22.

Duringthe fluid circulation for shutting-in the well, the manual choke 35 is used until the production fluids are circulated out and replaced with the weighting liquid. The production fluids generally include entrained gases which often cause the flow rates and pressures to vary substantially at the surface, possibly beyond the range of the capacity of the automatic choke to maintain the well under control. Thus, in order to minimize the possibility of blowouts with resulting fires, equipment damage, and fluid losses, the manual choke 35 is operated in the system by closing the valve in the branch return portion 640 and opening valve 71 in the branch line portion 64b so that all of the returning fluids in the line 64 are diverted from the return line 64 through the line 64b and the manual choke. The fluids flow from the line 64b into the discharge line 32 passing to the separator 32a with the liquids being returned to the tank 22.

The weighting liquid is circulated from the tank 22 through the manifold into the well and formation fluid is produced until the formation fluids have been completely displaced from the tubing strings 24 and 25 and replaced with the weighting liquid for establishing the desired pressure within the tubing strings at their lower ends to stabilize the well and to prevent production fluids from flowing from the well fonnations through the casing perforations 23a into the well.

While displacing the production fluids from the tubing strings by the weighting liquid, the manual choke 35 is adjusted in the usual manner to maintain sufficient back pressure on the well through the manifold to keep the well under control. The readout panel 33 and pressure recorder 34 provide visual indications of both the pressures and flow rates in the manifold input line 30a and the return line 64 so that the operator may constantly observe the flow conditions in both the fluid supply to the well and fluid return from the well and make the compensating adjustments in the back pressure by manipulation of the manual choke.

After the well is stabilized so that the desired conditions are established in the well, a well tool is pumped from the lubricator 44 through the tubing string 24 into the landing nipple 28 at the lower end of the tubing. The well too] is connected in a tool train including pumpable seal units and related equipment such as illustrated and described at pages 3,779-3,78l, The Composite Catalog of Oil Field Equipment and Services, 1966-67 Edition. The cap 45 on the lubricator 44 is removed, the tool train is inserted into the lubricator, and the cap is replaced. The valves of the manifold remain as adjusted for circulating the weighting liquid into the well through the flow line 24a and returning it through the flow line 25a. The liquid used for pumping the tool train into the well, which preferably is the same as the weighting fluid, is circulated from the tank 22 by the pump 31 through the lines 43 and 43a of the manifold into the lubricator behind the tool train, applying a pressure differential across the tool train forcing it from the lubricator through the flow line 24a into the tubing string 24. Since the well system is filled with liquid, the movement of the tool train from the lubricator through the flow line and tubing string displaces liquid in advance of the tool train through the flow line 24a, the tubing string 24, the crossover 27, and the tubing string 25 to the surface. The fluid returns to the manifold through the flow line 25a and the lubricator 62 and through the already described paths through the manifold back to the tank 22.

During the pumping of the tool train into the well it is preferred that production of formation fluids into the well through the perforations 23a and displacement of the circulating liquid outwardly into the formation through such perforations be held to a minimum. Thus, during the circulation ofthe liquid to move the tool train, the automatic choke 36 is util ized to impose a controlled back pressure on the well which maintains optimum bottom hole well conditions. The automatic choke is placed in operation in the system by closing the valve 71 in the return branch line portion 64b and opening the valve 70 in the branch line portion 6411 so that the returning fluid is directed through the automatic choke. The proper setting for the automatic choke is determined in the usual manner so that the choke controls the back pressure within a predetermined range for achieving optimum bottom hole well conditions which minimize fluid movement between the formation and the well during the liquid circulation procedure for moving the tool train from the surface to the desired position in the tubing string. As already explained, the setting of the automatic choke is accomplished by adjustments of the choke spring 91 for establishing the desired back pressure. The choke is preferably communicated with the return fluid pressure through the line 72a by adjustment of the valve 74 so that the pressure of the return fluid is monitored for maintenance of the desired back pressure by the choke. When a pressure increase in the return fluid is communicated through the line 72a into the chamber 92, the valve assembly is forced farther open against the spring 91 so that the back pressure is decreased. When the pressure in the returning fluid decreases sufficiently, as sensed in the chamber 92, the spring 91 forces the valve assembly back toward its seat, thus restricting flow through the valve until the forces of the spring and the control fluid pressure reach a balanced condition. In this manner, the position of the valve member of the choke fluctuates in response to the pressure communicated to it so that it regulates the back pressure within the desired predetermined range.

The tool train is pumped downwardly in the tubing string 24 until the well tool is seated in the landing nipple 28 at the lower end of the tubing string. Generally, the tool is then left in the landing nipple to discharge its particular function.

The elements of the tool train are disengaged from the well tool in the landing nipple 28 and are displaced back to the surface through the tubing string 24 and the flow line 24a into the lubricator 44 for removal from the well system. To pump the tool train back to the surface, the circulating fluid flow pattern is reversed so that the fluid is pumped into the well through the flow line 25a, as shown by the arrows in FIG. 2. The flow reversal is effected by closing the valve 50 in the line 43, opening the valves 52 and 54 in the connector lines 51 and 53, respectively, and closing the valve 60 in the connector line 55. The closed valve 50 diverts the fluid pumped into the input line 30a into the line 53 through which it flows to the line 61 since the closed valve 60 prevents flow into the line 55. The fluid is supplied through line 61 and the lubricator 62 into the flow line 25a through which it flows into and downwardly through the tubing string 25. The fluid crosses over into the tubing string 24 in the connection 27 so that the pressure is applied below the tool train for displacing the tool train upwardly through the tubing string 24. The fluid in the tubing string 24, the flow line 24a, and the lubricator 44 is displaced in advance of the upwardly moving returning tool train. The return flow follows the paths shown in FIG. 2, exiting from the lubricator 44 to the manifold through the line 43a into the connector line 51 in which it flows through the open valve 52 into the return line 64. The return fluids follow the already described path through the automatic choke 36 in the branch line portion 64a back through the separator into the tank 22. The fluid is circulated until the tool train has been returned into the lubricator 44. The pumping is then stopped, the pressure cap 45 on the lubricator is removed, and the tool train withdrawn. The pressure cap is replaced for such further fluid circulation or other well procedures as may be desired. During the return of the tool train to the surface the automatic choke 36 controls the back pressure on the system as already described.

The procedures already described for pumping a tool train from the lubricator 44 into the landing nipple at the lower end of the tubing string 24 are equally adapted to pumping a tool train from the lubricator through the flow line 25a and the tubing string 25 to the lower end of the tubing string 25. It will be evident that during the pumping of the tool train into the tubing string 25 the fluid input is through the lubricator 62 behind the tool train so that the flow pattern of FIG. 2 is employed. The return of the tool train from the tubing string 25 into the lubricator 62 is carried out by using the fluid flow pattern of FIG. 1 to pump the fluid downwardly into the tubing string 24 and through the crossover device 27 into the tubing string 25 below the tool train.

The automatic choke may be controlled in response to the input fluid pressure by setting the valve 74 to communicate the fluid pressure from the line 30a through the line 72b into the line 72 leading into the control fluid chamber 92 of the automatic choke. Since the input pressure required to overcome friction losses in circulating the fluid through the input leg of a well system, the tubing string 24 in the well 23, does not increase the pressure at the bottom of the hole and is thus not a factor in the back pressure held on the well, a correction factor is required which disregards the friction losses in such input leg when operating the automatic choke responsive to input pressure. In contrast, the friction losses in the return leg of the well flow system requires pressure at the bottom of the well which is imposed on the well formation and is a factor in the back pressure held on the well. If the tubing strings 24 and 25 have substantially identical frictional loss characteristics this correction factor is provided by use of an automatic choke having a valve assembly which has an effective area on its valve stem 85 within the control fluid chamber 92 between the ring seals 93 and 94 equal to substantially one-half the effective area in a choke designed for use in response to the fluid pressure on the return side of the system. If the friction losses in the two legs are not equal, the correction factor employed in adjusting the system is such as to disregard the friction losses in the input leg of the system.

The specific compact portable form of the manifold 21 shown in FIGS. 3-5, includes the same functional components denoted by the same reference numerals as already described and illustrated in schematic form in FIGS. 1 and 2. The portable manifold is supported on a skid 100 comprising a pair of spaced runners 101 secured together along opposite end portions by lateral members 102 and by plurality of lateral intermediate platform members 103. The manifold is secured by U-bolts 104 to channel-shaped mounting brackets 105 secured on the members 103. As best seen in FIG. 4, the manifold is supported along one side on a pair of spaced brackets 105 secured with the return line 64 and the branch line portion 64b. Similarly, the manifold is supported along the other side on the skid by a pair of spaced brackets 105 secured with the supply-return line 43a and the input line 30a. The supply-return line 61 also is supported on one of the brackets 105. The input and return lines 300 and 32 and the supplyreturn lines 43a and 61 are provided, respectively, with identical flanged couplings 30b, 32c, 43b, and 61a, respectively, for connecting the manifold into a well system as illustrated in FIGS. 1 and 2. The portable manifold is installed in the well system by connecting its flange couplings 43b and 61a with lines leading to the lubricators 44 and 42, respectively, and its input and return line couplings 30b and 320 with lines to the pump 31 and the separator 320, respectively. To conserve horizontal space, enhancing the portability of the skid mounted manifold, an over-and-under arrangement of the components as illustrated in FIGS. 3-5 has been employed. Generally, the manual and automatic chokes along with the branch return line portions in which they are connected are supported at a lower level on the skid while the connector lines 51, 53, and 55 along with portions of the lines 43, 61 and 64 are supported in close proximity at an upper level so that all the components of the manifold are nested together as a compact assembly which is readily movable between well locations. The readout panel 33 and pressure recorder 34, illustrated schematically in FIG. 3, are connected to and function with the manifold as already described.

Referring to FIGS. 6 and 7 the automatic choke 36, already broadly described, has the choke body 80 which. includes a spring housing section 120 enclosing the control spring 91, a cylinder section 121 including the control fluid pressure chamber 92, a valve housing section 122 in which the valve member 84 is movably disposed, and a seat and coupling section 123 which supports the annular valve seat 90 at its inward end and provides connection means at its outward or downstream end for a downstream portion of the branch line 64a into the choke.

The valve member of the choke is biased by the spring 91 toward a closed position at which an internal conical seat surface 90a of the seat 90 is engaged by a conical head seat surface 84a on the valve head member 84. The spring 91 is housed within the choke body section 120 and is compressed between an adjusting nut 124 and an external annular flange 125 on the valve stem 85. The adjusting nut has a handle 126 for rotating the nut to vary the compression of the spring. The nut has a blind bore 127 for receiving an end portion of the valve stem which telescopes into the nut when the valve member moves to an open position and when the spring is compressed to increase the force required to open the valve member. The body section 120 has a lateral port 131 so that the spring 91 and portion of the valve stem within the spring housing section operate under atmospheric pressure. A pair of ring seals 132 supported by the adjusting nut seal between the stem and the nut.

The valve member is biased open by control fluid communicated into the annular chamber 92 through the tubing 72 connected into a lateral internally threaded bore 140 in the body section 121 by a coupling 14]. The spaced ring seals 93 and 94 carried by the cylinder section 121 of the choke body seal with the longitudinal valve stem portions and 85b, respectively, to define the chamber 92. The valve stem portion 85b is smaller in diameter than the stem portion 851: so that an annular surface 100 is provided on the valve stem facing the valve seat exposed to control fluid pressure within the chamber 92 for biasing the valve assembly away from the valve seat toward open position. When the force of the control fluid pressure within the chamber 92 acting on the annular surface 100 of the valve stem exceeds the force exerted by the spring 91 on the valve stem flange 125, the valve stem is forced toward the spring moving the valve member 84 to a spaced position from the valve seat and opening the choke. Fluid entering the choke body through the lateral port 81 flows between the valve head member surface 84a and the valve seat 90a and through the bore 82 of the valve seat and coupling member into the downstream portion of the branch line portion 64a.

The valve assembly bore 85a provides a flow passage throughout the length of the valve assembly so that the pressure within the choke body downstream of the valve member 84 is communicated through the valve assembly into the bore 133 of the nut 124 along the outer end portion of the valve stem to equalize the pressures acting on the opposite end portions of the valve assembly.

The line of sealing between the valve head member face 84a and the valve seat face 90a is the same diameter as the line of sealing of the ring seals 94 with the valve stem so that the forces resulting from the pressure around the valve stem and the valve member 84 within the choke body between the seals 94 and the line of engagement of the faces 84a and 90a are balanced and do not bias the valve stem and valve member toward either closed or open position. Similarly, the line of sealing between the faces 84a and 90a is the same diameter as the line of sealing of the ring seals 132 with the valve stem within the adjusting nut so that balanced forces are imposed on the valve stem and member along opposite end portions resulting from the pressure within the choke downstream of the valve member as communicated through the flow passage 85a of the valve assembly. Thus, the downstream pressure in the choke does not tend to bias the valve assembly toward either closed or open position. The net forces affecting the opening and closing of the choke are therefore substantially limited to the force applied by the spring 91 to the valve stem and opposite force on the stem surface resulting from the controlled fluid pressure within the chamber 92 communicated from either the return conduit line 64 or the input conduit line 30a.

It will be recognized that other forms of pressure control means than the choke 36 may be used to provide a controlled back pressure on the well system responsive to the input of return fluid pressure.

The well system 20 has been described and illustrated as including the tubing strings 24 and 25 along with the crossover connection 27 so that fluid is supplied into and returned from the well through an exclusive U-shaped flow path in the well. The desired U-shaped flow pattern may also be obtained by other structural arrangements within a well, such as by the use of a single tubing string communicating at a desired location along its length with the tubing-casing annulus defined within the casing of the well around the tubing string. The tubing string functions as either an input or a return leg, and, similarly, the tubing-casing annulus serves as either an input or a return leg. Fluid may How in either direction as already explained. In such a well arrangement, tools are pumped into and out of the well in the single tubing string from a lubricator connected at the surface with the tubing string. The tubing string serves as the input flow passage and the tubing-casing annulus as the return flow passage during the pumping of the well tools into the well. The circulation pattern is reversed so that the tubing-casing annulus functions as the input flow passage with the tubing string serving as the return flow passage to pump the well too] back through the tubing string into the lubricator at the surface.

It will now be seen that a new and improved method for pumping well tools into and out of a well and performing other well servicing procedures has been described and illustrated.

It will be further seen that the method includes the use of supply and return flow passages connected with a surface manifold for supplying fluid under controlled flow conditions to the well flow passages for flow in either direction through such passages.

It will also be seen that the method includes the steps of providing input and return well flow passages, a manifold connected with such flow passages for controlling fluid flow conditions and direction in the well flow passages, pump means for supplying fluid under pressure to the manifold, a separator for segregating liquids and gases in the fluids returning from the manifold and a reservoir tank for storing returned liquids from the manifold for reinjection into the flow passages of the well system.

It will also be seen that a new and improved method of operating a well has been described and illustrated for supplying well fluid to a well flow passage system under controlled conditions and for flow in either direction through such well flow passages.

It will be further seen that the method includes manual and automatic choke means for imposing a controlled back pressure in fluids flowing in the manifold.

It will be further seen that a new and improved method of circulating fluids in a well has been described and illustrated which includes supplying fluids to and returning fluids from a well without either producing formations fluids from the well or forcing the circulating fluids into formations communicating with the well.

It will be further seen that in accordance with one aspect of the invention production is terminated and the well is stabilized by filling the well with a weighting fluid for partially or.

completely counterbalancing well pressure to prevent production fluids flowing into the well, and a well tool is introduced into the well by pumping the tool through one flow passage in the well while returning fluid within the well in advance of the tool to the surface through another flow passage in the well while the return flow pressure is maintained at a value which produces bottom hole pressure conditions in the well which minimize flow between the well and the formation surrounding the well.

FIGS. 1A and 2A illustrate an alternate simplified form of fluid circulation control manifold 21A which may be used in situations where flow conditions, and in particular pressure conditions, permit the use of valves, such as three-way valves which are normally employed at lower pressures than the valves of the type shown in the manifold 21 in FIGS. 1 and 2. With the exception of the flow direction control features of the manifold 21A, all other features of the manifold and of a well system with which it is used are identical to those shown in FIGS. 1 and 2 and already described, and thus components common to both systems and manifolds are referred to by the same reference numerals as used in FIGS. 1 and 2. A threeway valve 200 is connected to the discharge end of the input line 30a downstream of the pump 31 and the flow meter 42, shown only in FIGS. 1 and 2. First and second connecting conduit lines 201 and 202 are each connected at one end into the valve 200 so that the valve selectively directs fluid from the input line into either of the connecting lines. A second threeway valve 203 is connected with the other end of the first and second connecting lines and with the input end of the return line 64 which leads to the manual and automatic chokes 36 as shown in FIGS. 1 and 2. The valve 203 selectively directs fluid into the return line from either of the connecting lines. The discharge-return line 43a is connected at one end into the lubricator 44 and at the other end to the first connecting line 201. Similarly, the discharge-retum line 61 is connected at one end to the lubricator 62 and at the other end to the second connecting line 202.

When the valves 200 and 203 are positioned as shown in FIG. 1A fluid delivered to the manifold through the input line is directed by the valve 200 into the first connecting line 201. The input fluid flows through the first connecting line into the conduit line 43a. From the line 43a the fluid flows through the lubricator 44 into the well system as shown in FIG. 1. The fluid returning from the well system flows through the lubricator 62 and the conduit line 61 into the second connecting line 202. It flows through the valve 203 into the return line 64 following the already described paths back to the tank 22 as shown in FIG. 1. Flow in the opposite direction through the manifold and the well system is obtained by positioning the valve 200 and 203 as shown in FIG. 2A. The input fluid flows through the valve 200 into the second connecting line 202 from which it flows to the lubricator 62 through the conduit line 61. The return fluid from the well system flows from the lubricator 44 through the conduit line 43a into the first connecting line 201. The fluid flows from the first connecting line through the valve 203 into the return line 64 and on to the tank 22 through either of the chokes, as already discussed.

It will now be seen that where flow conditions permit a more simplified manifold may be employed utilizing a reduced number of valves for controlling the direction of flow of the input and return fluids through the manifold.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

l. A method of manipulating a well tool in a well through a tubing string disposed in said well, said tubing string defining a first flow passage in said well, and said well being provided with a second flow passage communicating within said well with said first flow passage, said method comprising: inserting said well tool into said tubing string at the surface end of said string; pumping fluid into said tubing string behind said well too] displacing said well too] through said tubing string into said well, fluid flowing in said tubing string ahead of said well tool to the surface through said second well flow passage; and controlling the return fluid flow pressure from said well in said second flow passage to maintain the pressure in said fluid at the bottom of said well at a pressure level minimizing fluid flow at the bottom of said well between said well and formations around said well in communication therewith.

2. A method of manipulating a well tool in accordance with claim 1 including returning said well too] to the surface from said well by reversing the direction of flow of said fluid in said well passages comprising pumping said fluid into said second flow passage of said well displacing said well tool and fluid ahead of said well tool through said tubing string back to the surface while controlling the return fluid flow pressure ahead of said well tool to maintain the fluid pressure within said well at said optimum value.

3. A method of manipulating a well too] as defined in claim 2 in a production well including stabilizing said well preliminary to introducing said well tool into said tubing string by circulating liquid through said well flow passages until said well is substantially filled with said liquid to develop a hydrostatic pressure in said well at least partially counterbalancing the bottom hole pressure of said well including flowing fluids returning from said well through a variable restriction and varying said restriction to limit the return fluid flow pressure from said well to a predetermined value for maintaining control of said well until production fluids in said well for passages are circulated out of said passages and replaced by said liquid.

4. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first string and up a second string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises:

maintaining said selected pressure on said fluid material in said formation by varying the back pressure on the fluid pumped up the second string in response to variations in the flow rate of fluid in said circulation path;

a well tool being pumped through one of said strings by said fluid while said fluid is pumped through said circulation path; and

thereby maintaining said selected fluid pressure on said formation.

5. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first tubing string and up a second tubing string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises: pumping fluid into said first tubing string at the surface downwardly in the well and upwardly from the well to the surface through said second tubing string; monitoring the pressure and flow rate of fluid pumped into said first tubing string at the surface; moni toring the pressure and flow rate of the fluids flowing from said second tubing string at the surface; determining from said monitored pressures and flow rates a back pressure to be applied to said fluids pumped through said tubing strings to maintain a selected fluid pressure on the fluid material in said formation; maintaining said selected fluid pressure back pressure on said fluid material in said formation by varying said back pressure at the surface on the fluid pumped up the second string determined in accordance with the monitored pressures and flow rates of the fluids in said circulation path.

6. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first tubing string and up a second tubing string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises: pumping fluid into said first tubing string at the surface downwardly in the well and upwardly from the well to the surface through said second tubing string; monitoring the pressure and flow rate of fluid pumped into said first tubing string at the surface; monitoring the pressure and flow rate of the fluids flowing from said second tubing string at the surface; determining from said monitored pressures and flow rates a back pressure to be applied to said fluids pumped through said tubing strings to maintain a selected fluid pressure on the fluid material in said formation; maintaining said selected fluid pressure back pressure on said fluid material in said formation by varying said back pressure at the surface on the fluid pumped up the second string determined in accordance with the monitored pressures and flow rates of the fluids in said circulation path; circulating fluid through the tubing string of the circulation path to provide a body of fluid of substantially uniform density in said tubing string of said circulating path; and pumping a well tool through one of said tubing strings by circulating said body of fluid through said tubing strings.

7. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first tubing string and up a second tubing string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises: pumping fluid into said first tubing string at the surface downwardly in the well and upwardly from the well to the surface through said second tubing string; monitoring the pressure and flow rate of fluid pumped into said first tubing string at the surface; monitoring the pressure and flow rate of the fluids flowing from said second tubing string at the surface; determining from said monitored pressures and flow rates a back pressure to be applied to said fluids pumped through said tubing strings to maintain a selected fluid pressure on the fluid material in said formation; main taining saidselected fluid pressure back pressure on said fluid material in said formation by varying said back pressure at the surface on the fluid pumped up the second string determined in accordance with the monitored pressures and flow rates of the fluids in said circulation path; recording the pressure and flow rate of fluid pumped into said first tubing string; recording the pressure and flow rate of fluid flowing to the surface through said second tubing string; regulating the flow through the tubing strings in the well by maintaining a back pressure on the fluids flowing from the well at a value determined from the recordings to prevent flow of circulated fluids into the well formation and to prevent flow of fluids from the well formation into the circulated fluid in the circulation path.

8. A method of manipulating a well tool in a well through a tubing string disposed in said well, said tubing string defining a first flow passage in said well and said well being provided with a second flow passage communicating within said well with said first flow passage, said method comprising: inserting said well tool into said tubing string at the surface end of said tubing string; pumping fluid into said tubing string behind said well tool displacing said well tool through said tubing string into said well; flowing fluid in said tubing string ahead of said well tool to the surface through said second flow passage; monitoring the pressure and flow rate of fluid pumped into said tubing string and the pressure and flow rate of fluid flowing to the surface through said second flow passage; and controlling the pressure of the return fluid flowing from said well in said second flow passage to maintain the pressure of said fluid at the bottom of said well at a desired pressure level minimizing fluid flow at the bottom of said well between said well and producing formations around said well in communication therewith.

9. A method of the character set forth in claim 8 including: recording the pressure and flow rate of the fluids pumped into said tubing string and the pressure and flow rate of fluids flowing to the surface through said second flow passage for use in controlling the pressure of return fluid flowing from said well.

10. A method of manipulating a well tool in accordance with claim 8 including: returning said well too] to the surface from said well by reversing the direction of flow of said fluid in said well passages by pumping said fluid into said second flow passage of said well displacing said well tool and fluid in said tubing string above said well tool through said tubing string back to the surface; controlling the pressure of the return fluid flowing ahead of said well tool to maintain the fluid pressure within said well at said desired value.

11. A method of manipulating a tool as defined in claim 8 including: stabilizing said well preliminary to introducing said well tool into said tubing string by circulating liquid through said well flow passages until said well is substantially filled with said liquid to develop a hydrostatic pressure in said well at least partially counterbalancing the bottom hole pressure of said well; monitoring the pressure and flow rate of fluid pumped into said tubing string and the pressure and flow rate of fluid flowing to the surface through said second well flow passage; flowing fluids returning from said well through a variable restriction; and varying said restriction to limit the pressure of the return fluid flowing from said well to a predetermined value determined by said monitoring step for maintaining control of said well until production fluid in said well flow passages are circulated out of said passages and replaced by said liquid.

12. A method as set forth in claim 11 including: recording the pressures and flow rates monitored during the pumping of the fluids into the well and the flow of the fluid out of the well and varying the restriction for varying the flow of fluids from the well in accordance with the recorded monitored pressure and flow rates of fluids monitored and recorded.

Disclaimer and Dedication 3,637,012.Phillip S. Sizer, Dallas, and Harry E. Sehwegman, Richardson, TeX. WELL FLOW CIRCULATING METHODS. Patent dated Jan. 25, 1972. Disclaimer and dedication filed Mar. 9, 1972, by the assignee, Otis Engineering Corporation. Hereby enters this disclaimer to claims 1, 2, S and 4 and dedicates the remainder of the term to the Public.

[Ofiieial Gazette November 14, 1972.] 

1. A method of manipulating a well tool in a well through a tubing string disposed in said well, said tubing string defining a first flow passage in said well, and said well being provided with a second flow passage communicating within said well with said first flow passage, said method comprising: inserting said well tool into said tubing string at the surface end of said string; pumping fluid into said tubing string behind said well tool displacing said well tool through said tubing string into said well, fluid flowing in said tubing string ahead of said well tool to the surface through said second well flow passage; and controlling the return fluid flow pressure from said well in said second flow passage to maintain the pressure in said fluid at the bottom of said well at a pressure level minimizing fluid flow at the bottom of said well between said well and formations around said well in communication therewith.
 2. A method of manipulating a well tool in accordance with claim 1 including returning said well tool to the surface from said well by reversing the direction of flow of said fluid in said well passages comprising pumping said fluid into said second flow passage of said well displacing said well tool and fluid ahead of said well tool through said tubing string back to the surface while controlling the return fluid flow pressure ahead of said well tool to maintain the fluid pressure within said well at said optimum value.
 3. A method of manipulating a well tool as defined in claim 2 in a production well including stabilizing said well preliminary to introducing said well tool into said tubing string by circulating liqUid through said well flow passages until said well is substantially filled with said liquid to develop a hydrostatic pressure in said well at least partially counterbalancing the bottom hole pressure of said well including flowing fluids returning from said well through a variable restriction and varying said restriction to limit the return fluid flow pressure from said well to a predetermined value for maintaining control of said well until production fluids in said well for passages are circulated out of said passages and replaced by said liquid.
 4. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first string and up a second string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises: maintaining said selected pressure on said fluid material in said formation by varying the back pressure on the fluid pumped up the second string in response to variations in the flow rate of fluid in said circulation path; a well tool being pumped through one of said strings by said fluid while said fluid is pumped through said circulation path; and thereby maintaining said selected fluid pressure on said formation.
 5. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first tubing string and up a second tubing string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises: pumping fluid into said first tubing string at the surface downwardly in the well and upwardly from the well to the surface through said second tubing string; monitoring the pressure and flow rate of fluid pumped into said first tubing string at the surface; monitoring the pressure and flow rate of the fluids flowing from said second tubing string at the surface; determining from said monitored pressures and flow rates a back pressure to be applied to said fluids pumped through said tubing strings to maintain a selected fluid pressure on the fluid material in said formation; maintaining said selected fluid pressure back pressure on said fluid material in said formation by varying said back pressure at the surface on the fluid pumped up the second string determined in accordance with the monitored pressures and flow rates of the fluids in said circulation path.
 6. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first tubing string and up a second tubing string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises: pumping fluid into said first tubing string at the surface downwardly in the well and upwardly from the well to the surface through said second tubing string; monitoring the pressure and flow rate of fluid pumped into said first tubing string at the surface; monitoring the pressure and flow rate of the fluids flowing from said second tubing string at the surface; determining from said monitored pressures and flow rates a back pressure to be applied to said fluids pumped through said tubing strings to maintain a selected fluid pressure on the fluid material in said formation; maintaining said selected fluid pressure back pressure on said fluid material in said formation by varying said back pressure at the surface on the fluid pumped up the second string determined in accordance with the monitored pressures and flow rates of the fluids in said circulation path; circulating fluid through the tubing string of the circulation path to provide a body of fluid of substantially uniform density in said tubing string of said circulating path; and pumping a well tool through one of said tubing strings by circulating said body of Fluid through said tubing strings.
 7. In a well provided with at least two interconnected tubing strings providing a circulation path for fluid pumped down a first tubing string and up a second tubing string in which a fluid material is being held in a formation in communication with said well by application of a selected fluid pressure on said formation, the method which comprises: pumping fluid into said first tubing string at the surface downwardly in the well and upwardly from the well to the surface through said second tubing string; monitoring the pressure and flow rate of fluid pumped into said first tubing string at the surface; monitoring the pressure and flow rate of the fluids flowing from said second tubing string at the surface; determining from said monitored pressures and flow rates a back pressure to be applied to said fluids pumped through said tubing strings to maintain a selected fluid pressure on the fluid material in said formation; maintaining said selected fluid pressure back pressure on said fluid material in said formation by varying said back pressure at the surface on the fluid pumped up the second string determined in accordance with the monitored pressures and flow rates of the fluids in said circulation path; recording the pressure and flow rate of fluid pumped into said first tubing string; recording the pressure and flow rate of fluid flowing to the surface through said second tubing string; regulating the flow through the tubing strings in the well by maintaining a back pressure on the fluids flowing from the well at a value determined from the recordings to prevent flow of circulated fluids into the well formation and to prevent flow of fluids from the well formation into the circulated fluid in the circulation path.
 8. A method of manipulating a well tool in a well through a tubing string disposed in said well, saId tubing string defining a first flow passage in said well and said well being provided with a second flow passage communicating within said well with said first flow passage, said method comprising: inserting said well tool into said tubing string at the surface end of said tubing string; pumping fluid into said tubing string behind said well tool displacing said well tool through said tubing string into said well; flowing fluid in said tubing string ahead of said well tool to the surface through said second flow passage; monitoring the pressure and flow rate of fluid pumped into said tubing string and the pressure and flow rate of fluid flowing to the surface through said second flow passage; and controlling the pressure of the return fluid flowing from said well in said second flow passage to maintain the pressure of said fluid at the bottom of said well at a desired pressure level minimizing fluid flow at the bottom of said well between said well and producing formations around said well in communication therewith.
 9. A method of the character set forth in claim 8 including: recording the pressure and flow rate of the fluids pumped into said tubing string and the pressure and flow rate of fluids flowing to the surface through said second flow passage for use in controlling the pressure of return fluid flowing from said well.
 10. A method of manipulating a well tool in accordance with claim 8 including: returning said well tool to the surface from said well by reversing the direction of flow of said fluid in said well passages by pumping said fluid into said second flow passage of said well displacing said well tool and fluid in said tubing string above said well tool through said tubing string back to the surface; controlling the pressure of the return fluid flowing ahead of said well tool to maintain the fluid pressure within said well at said desired value.
 11. A method of manipulating a tool as defined in claim 8 including: stabilizing said well preliminary to introducing said well tool into said tubing string by circulating liquid through said well flow passages until said well is substantially filled with said lIquid to develop a hydrostatic pressure in said well at least partially counterbalancing the bottom hole pressure of said well; monitoring the pressure and flow rate of fluid pumped into said tubing string and the pressure and flow rate of fluid flowing to the surface through said second well flow passage; flowing fluids returning from said well through a variable restriction; and varying said restriction to limit the pressure of the return fluid flowing from said well to a predetermined value determined by said monitoring step for maintaining control of said well until production fluid in said well flow passages are circulated out of said passages and replaced by said liquid.
 12. A method as set forth in claim 11 including: recording the pressures and flow rates monitored during the pumping of the fluids into the well and the flow of the fluid out of the well and varying the restriction for varying the flow of fluids from the well in accordance with the recorded monitored pressure and flow rates of fluids monitored and recorded. 